Impact of the protein composition on the structure and viscoelasticity of polymer-like gluten gels

TL;DR

This study explores how the protein composition of gluten influences the structure and viscoelastic properties of polymer-like gluten gels, revealing the critical role of glutenin content and hydrogen bonding in gel behavior.

Contribution

It uncovers the link between protein assembly structures in dilute solutions and the gel's mechanical properties, highlighting the importance of glutenin enrichment and hydrogen bonds.

Findings

Protein assemblies are present only in glutenin-rich mixtures.

Viscoelasticity correlates with the amount of hydrogen-bonded domains.

Structural features in dilute solutions predict gel behavior.

Abstract

We investigate the structure of gluten polymer-like gels in a binary mixture of water/ethanol, $50/50$ v/v, a good solvent for gluten proteins. Gluten comprises two main families of proteins, monomeric gliadins and polymer glutenins. In the semi-dilute regime, scattering experiments highlight two classes of behavior, akin to standard polymer solution and polymer gel, depending on the protein composition. We demonstrate that these two classes are encoded in the structural features of the proteins in very dilute solution, and are correlated with the presence of proteins assemblies of typical size tens of nanometers. The assemblies only exist when the protein mixture is sufficiently enriched in glutenins. They are found directly associated to the presence in the gel of domains enriched in non-exchangeable H-bonds and of size comparable to that of the protein assemblies. The domains are probed in neutron scattering experiments thanks to their unique contrast. We show that the sample visco-elasticity is also directly correlated to the quantity of domains enriched in H-bonds, showing the key role of H-bonds in ruling the visco-elasticity of polymer gluten gels.